利用元胞自动机和有限差分（ CA－FD）法，采用宏－微观两种尺度，将宏观温度场与微观枝晶生长过程耦合在一起，再现了Fe－0．06％C二元合金焊接熔池的凝固过程．同时，探讨了边界散热速率对焊接熔池中枝晶生长形貌及晶粒尺寸的影响；分析了形核基底数与枝晶生长间的关系；并用实验对模拟结果进行了验证．结果表明，在熔池凝固过程中，温度梯度沿散热边界向绝热边界方向不断减小，等温线弧度不断增大；熔池散热边界附近的液相中溶质浓度远远高于绝热边附近和模拟区域中心的液相溶质浓度；模拟区域内的温度梯度随着边界散热速率的增大而升高．此外，随着形核基底的增加，柱状晶数量基本不变；而等轴晶数量不断增多，分布范围逐渐扩大，但尺寸有所减小．模拟结果反映了焊接熔池的凝固过程，并与实验结果吻合，为实际焊接工艺的选取提供了一定的参考．
The simulation model of macroscopic temperature field and dendritic growth, in which cellular automata?finite difference( CA-FD) methods and two kinds of scales are adopted, are combined to simulate the solidification process of Fe-0.6%C alloy in welding pool. According to the model, the influence of dendrite morphology and grain size with different boundary cooling rate and different nucleation basal are analyzed and discussed. To verify the simulation results, welding experiments are carried out. It is found that in the solidification process the temperature gradient decreases while isotherm curvature increases from the cooling side to the adiabatic side. Meanwhile, the solute concentration near the cooling side is much higher than that near the insulation boundary and in the center of the welding pool. Furthermore, the region of temperature gradient rises with the increase of cooling rate. As the nucleation substrate increases, the number of columnar crystals remains the same, while the amount of equiaxed crystals raise faster. The simulation results demonstrate the solidification process of welding pool and agree well with the experimental results.
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